Electrical heating element



P. F. APFEL.

ELECTRICAL HEATING ELEMENT.

APPLICATION FILED APR.26|1919.:

1,337,633. Patented Apr. 20, 1920.

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PHILIP F. APFEL, OF SEATTLE, WASHINGTON.

ELECTRICAL HEATING ELEMENT.

Specification of Letters Patent.

Patented Apr. 20, 1920.

Application filed April 26, 1919. Serial No. 293,290.

electric heating elements of the class that are adapted to be immersed in a body of liquid for heating the same and to improvements in methods of making the same, and the object of my invention is to provide an electric heating element that is simple in its form of construction and inexpensive to manufacture and that is durable and eflicient when subjected to use.

A further object is to provide an electric heating element that is composed of a double coil of wire and that is extensible so that it may be made to fit either a large or small receptacle.

A still further object is to provide an electric heating element that is so constructed as to practically eliminate the danger of the conductor wires becoming short circuited.

With the above and other objects in view which will appear as the description proceeds, my invention resides in the combination and arrangement of parts and in the details of construction hereinafter described and claimed I accomplish these objects by devices illustrated in the accompanying drawings, wherein Figure I is a view in elevation of a heating element embodyin my invention after it is made up and be ore it is wound into the form of a coil;

Fig. 2 is an enlarged view in crosssection on broken line 2, 2 of Fig. 1;

Fig. 3 is a view in elevation of one of my heating elements in an extended position as it may appear when installed in a relatively long tank, the tankibemg shown in crosssectlon; and

Fig. 4 is a. view in elevation of the same element in a contracted position as it may appear when installed in a relatively short tank, the tank being shown in cross-sectlon.

My heating element is constructed by takin a piece of soft flexible metallic con- 66 duit, drawinga piece of high resistance insulated wire into said conduit, contracting the condult on to the insulated wire by drawlng the conduit through a die, bending the conduit double and then winding such conduit into an extensible coil.

1 am aware that heating elements have been made by doubling an insulated circuit Wire, then inserting it in a soft metal conduit and then forming a coil but this form of construction is objectionable because it necessitates having two insulated circuit wires in the same con-duit thereby makin an element that is easily short circuited an one whereln it is practically impossible to exclude air spaces and to secure uniformly tight contact between the insulated wires and the walls of the conduit.

Referring to the drawings, throughout which like reference numerals indicate like parts, the numeral 5 designates a conduit preferably of soft metal, as a composition of lead or copper, that is capable of being bent into any desired shape and 6 designates a high resistance electric circuit wire that is inclosed in a jacket 7 of refractory insulating material and is inserted within the conduit 5 In the construction of my heating element the insulated wire is fished through or otherwise inserted in the conduit 5 while the latter is straight and the conduit 5 is then drawn through a die of a diameter smaller than the external diameter of the conduit to contract the same tightl about the insulation 7 of the wire 6 an insure that no air spaces remain between the insulation and the inner walls of the conduit, which conduit is then bent double, as shown in Fig. 1

and the ends of the wires 6 are projected.

through a cap member 8 that is arranged to fit over and close an opening 10 in the top of the tank 11 or 12 as shown in Figs. 3 and 4.

After the conduit 5 has been doubled, as shown in Fig. 1, it may be wound intoa coil, as shown in Figs. 3 and f1; such con-- duit preferably being wound in the form of a substantially closed coil as shown in Fig. 4 and then being stretched or elongated into the form shown in Fig. 3, if it is desired to use such element in the relatively deggp tank 11.

y constructing a heating element wherein only one circuit wire is disposed within each conduit the danger of short circuits is eliminated and the durability and eificiency of the coil is greatly increased.

The coil herein disclosed is simple and inexpensive in construction, easy to install and may be extended to fit a vessel of any desired length.

It is obvious that chan es in the precise form of construction an arrangement of the parts of my invention may be resorted to within the scope of the following claim.

' What I claim is:

An electric heatin element comprising a resistance element 0 double strand formation bent to spiral form with two independent slightly spaced strands in each coil 15 of the spiral form, whereby the spirals may be lengthened and shortened to accommodate the heating element to vessels of different depths, the strands adjacent the coil being twisted, and a mounting cap carried by the heating element intermediate the coil and twisted portion for suspending the coil within the open upper end of a container.

In witness whereof I hereunto subscribe my name this 19th da of A ril, A. D. 1919. 25

P ILI F. APFEL. 

